C.W. Mays
~ gel?
estimated (Weaver,
iodine 129 chain,
e “endix - contd..
et.al) at about 3.0 per cent for the
and 4.6 per cent for the iodine 131
chain, from plutonium 239 fission by fission-spectrum
neutrons. “° Thus, there are about 2.4 x 10+
O
atoms of
iodine 129 associated with an initial iodine 151 activity
of one microcuri:.
To assay iodine 129 it can be activated to iodine 140
by neutron bombardment.??
A saturation activity of 73
disintegrations per second of iodine 130 (easily counted)
results from the bombardment of 2.4 x 10
LO
atoms of
iodine 129 (cross-section 30 x 107 24 ome per atom) by a
flux of 10 14 neutrons per om* each second. 19
Iodine 129 atoms are removed from the adult human
thyroid with a biological half-time of about three months,
although this varies from person to person.“ Therefore,
the appropriate thyroid samples would be from thyroid
tissue obtained after a nuclear test of interest,
Additional pathological samples obtained just prior to
the test of interest would be needed to correct for
environmental icdine 129.
In this connection, note that
little stratospheric fallout was present during the
1951-55 tests for which dose estimates are most urgently
needed.
James Arnold (Kansas City General Hospital, Kansas
City, Missouri) has pointed out that if milk samples
taken from contaminated areas at the time of contamination
can be located, these might be suitable for iodine 129
analysis.
A final suggestion:
it might be possibleto use
strontium 90 or cesium 137 as radioactive indicators.
All
are retained cn pasture vegetation with a biological
half-time of about thirteen days. ee
All are absorbed by
the cow, transferred to milk and assimilated by man.
Strontium 90 has the advantage that it is not vaporized
during sample ashing.
Cesivm 137 is easily detected
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